Stihl Chainsaw Spark Plug Gap – All You Need To Know


To ensure the combustion in your chainsaw engine, a spark plug is a key to igniting the air-fuel mixture inside the cylinder. While using the chainsaw, users face the problem of spark plug gaps frequently.

Let us inform you that the gap between the electrode and periodic replacement is crucial for engine performance.

This gap is known to be the spark plug gap. In a Stihl chainsaw, the spark plug gap is normally 0.020. For other chainsaws, the gap varies. The most usual gap is 0.025.

Let’s see how the gap ensures your Stihl chainsaw run, the problems with the gap, and all the details you need to know about Stihl chainsaw spark plug gap.

What is The Spark Plug Gap, And Why Is It Important?

Spark plugs are simple in design. The structure is not complex to understand. Who else doesn’t want the engine of his chainsaw running well?

But you can’t imagine running a chainsaw engine without a spark plug. And though the gap between the electrodes in a spark plug seems silly and unimportant, let us enlighten you on how much work this little Mr. Gap does.

Suppose the gap between the centre and the electrodes is too small, and you try to run your chainsaw engine.

What happens next?

Your chainsaw engine can miss the fire or run haphazardly. Sometimes, the incorrect gap can cause unwanted firing and delay combustion.

What Happens If The Gap Is Excessive on The Contrary To The Normal Gap?

Your chainsaw engine will not start; sometimes, it results in cylinder misfiring. A few other cases like black spark plug, rough idle, and wet spark plug are also found.

The wider gap causes the unwanted flame to the engine. And the gap may increase over time while you continue running your Stihl chainsaw for a long time.

It is normal to face the problem with the spark plug. Make sure that you check out the spark plug gap regularly and clean the gap. Also, ensure that the gap is accurate. Sometimes you may need to shorten the gap too!

Stihl Chainsaw Spark Plug Gap – Symptoms Checking 

Most of the chainsaws have a 0.025 gap in their spark plug. Different manufacturers make different kinds of chainsaws. However, the basic structure is constant.

The Stihl chainsaw engine has a spark plug with a gap of 0.020 between the side electrodes and the center. To check the spark plug gap of a Stihl chainsaw, you need to follow a few steps.

Symptoms Of Incorrectly Gapped Spark Plug

Incorrectly gapped spark plug causes engine issues like an unwanted flame from the engine, excessive firing, delay in starting the engine or poor fuel performance.

Let’s point out some more:

1. Poor Engine Performance

Every step stroke engine performs at an optimal level. To ensure the engine performance, the gap must be according to the manufacturing company’s instructions. An incorrect gap results in a haphazard spark and delays the combustion.

2. Engine Knocking

Also termed engine pinging is an indication that the spark plug gap is not correct. This will again cause the engine to delay the spark and weaken the engine performance.

3. Unwanted Flame

The proper gap between the electrodes and the center ensures that the ignition system is okay. When the spark plug is not properly gapped, you may find some unusual flame coming from the engine.

4. Rough Engine Idle

Irregular and rough idle in an engine refers to the defaults with the spark plug. But let us inform you that just check the spark plug gap, and you will find your problem.

5. Engine Hesitation

In a two-stroke engine, sometimes it fumbles or hesitates during acceleration. Don’t worry; check out the spark plug gap, and there hides your crisis.

When the gap is more than usual, the ignition spark can’t manage the strength as it has to run through the ‘extra gap”. This results in engine hesitation!

How To Test/Check Spark Plug Gap In Stihl Chainsaw?


When you install a new spark plug in your Stihl chainsaw engine, never forget to check the gap between the side electrodes and the center.

This is the first precaution. But when your chainsaw engine shows the symptoms that we discussed above, let’s first check if the gap is accurate.

To check the gap:

  • Pull out the spark plug from the boot adjacent to the engine cover.
  • Clean the spark plug with a piece of a soft cloth.
  • Primarily, try to read the spark plug color to check out if the spark plug parts are okay.
  • If you don’t know how to read the spark plug, you can check our other guides regarding the topic.

After ensuring the spark plug is active otherwise, let’s now check out the gap. There are a few tools available in the market known as “spark plug checker” that will help you to determine the gap.

Usually, a tool such as the picture below is used to check the gap. This was an ideal tool used to measure and set the gap over the years.

But we recommend you use a wire-style tool. It is easy to use and smarter than the coin-style one.

Let us introduce another type of gap tool. It’s called a feeler gauge type gapper. After choosing the perfect tool, let’s check the gap.

To check the gap, you need to put the wire looms into the spark plug gap and check if the gap properly adjusts to the looms with a measurement of 0.020. If it perfectly adjusts with the looms, then the spark plug gap is accurate.

But if you hardly can fill the gap, it seems tight, or the loom can easily pass through the gap, then the spark plug is inaccurately gapped.

How To Set The Gap Of A Spark Plug?

Listen up carefully; you can set the spark plug using a different kind of gapper available in the market.

You can use the wire looms or a set of feeler gauges. Let’s choose one, and the basic theory of gapping the spark plug is the same. But it is easier to gap the spark plug by using the wire looms tool.

If it is mandatory to adjust the gap, you can easily increase or shorten the tool’s gap. Make sure you properly adjust the gap. A little bit more or less gap can bring a huge difference to engine performance.

When you can’t find the wire looms tool, try the other tool, the set feeler gauges. To adjust the gap, you need to hold the spark plug with strong support to ensure that you can keep your hand free.

After checking the gap, use a hammer to shorten the gap if the gap is lower than the accurate one.

Be careful so that you do not break the electrodes. This is a very unusual way. But you never know, this may be useful sometimes.

Now, remember one thing. It’s a wise decision to avoid a coin-style tool to enlarge the gap.


Because, most of the time, they break the tip while you are trying to increase the gap measurement. In case you have broken the tip of the spark plug, never think of using it again.

Which Spark Plug is Suitable For Your Stihl Chainsaw?

A spark plug is important for a two-stroke engine like a chainsaw. Besides, a petrol power tool like a Stihl chainsaw requires a perfect and flawless spark plug.

In Stihl chainsaws, you will find an NGK spark plug automatically set in the engine. The best spark plugs we can recommend you to use in your Stihl chainsaw are as follows:

This is the most popular and probably the best spark plug for the Stihl chainsaw engine. This is affordable and available in the market. Most of the Stihl engine is comfortable with the NGK.

Champion is a popular brand found in China. This spark plug is also affordable and has maximum customer reviews.

Bosch produces spark plugs with 26 different electrode layouts. If you don’t want to waste your money on the expensive plug, you can easily afford this one for your still chainsaw engine.


Do Spark Plug Gaps Increase Over Time?

In most cases, the gap is reduced after a long time of use. In a chainsaw, a wider gap in the spark plug generates an unusual flame from the engine.

If the chainsaw is run at a varying speed (too slow/too fast), the gap between the side electrodes and the center may be increased.

How Often Do I Need To Change The Spark Plug In My Stihl Chainsaw?

There is no exact time duration for the change of the spark plug. You need to check the spark plug, read it properly, and test the gap when any problem is found with the engine or spark.

A spark plug may serve you 10 to 12 years if your engine has a friendly relation with the spark plug.

Again if you are using your chainsaw more frequently, you may need to change the spark plug regularly. We recommend you change the spark plug immediately after your chainsaw is getting difficult to start.

Chainsaw Spark Plug Gap: What Is It?

Wrapping Up: 

An incorrect spark plug gap can make your Stihl chainsaw stop. If you find your chainsaw’s spark plug improperly gapped, don’t throw it in the trash for the first instance.

Make sure you follow the whole guide we provided to check and set the proper gap in your chainsaw.

If you want to avoid unwanted problems with the spark plug, enlighten yourself on the Stihl chainsaw spark plug gap and how you can maintain a spark plug.

Before we conclude, here’s a tip for you; proper maintenance of spark plug will reduce the haphazard you can face regarding spark plug!

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